Pilots of aircraft require a safe and reliable method to navigate to an airport and access a runway for landing. Visual flight rules (VFR), while at times preferable, are insufficient to allow a pilot to navigate and land in all weather conditions. For example, a pilot may be navigating to an airport at some distance from the originating airport and may encounter varying weather and landing conditions which limit visibility and make a VFR landing too treacherous. Because of limited fuel and other factors, a pilot must be able to land his aircraft even when VFR approach and landing methods are not practical. Therefore, procedures have been developed for instrument flight rules (IFR) navigation and landing. Such procedures are typically more dangerous and more complicated due to a reliance on numerous instruments within a cockpit and the inability to use visual cues from outside the aircraft. To enhance safety, approach and landing procedures may be defined by a series of rules and requirements identified and promulgated by an aviation regulating authority (e.g., Federal Aviation Administration). Pilots must understand that it is important that these procedures be strictly followed to avoid potential disaster.
Each runway at an airport may have different navigational aids available configured to facilitate IFR approach and landing methods on the particular runway. These navigational aids may include equipment related to, for example, non-directional beacon (NDB), VHF Omni-directional Radio (VOR), Global Positioning System (GPS), Localizer (LOC), and Instrument Landing System (ILS) approaches. Therefore, when flying an instrument approach, a pilot must be familiar with all of the possible approach methods for a particular runway and the related, available equipment. For example, during a VOR approach to a particular runway, a pilot may not be provided distance information if distance measuring equipment (DME) is disabled or not present. Therefore, the approach must be timed from a known fix with distance information calculated based on the time, aircraft velocity, and navigational charts. Such a task may substantially increase a pilot's cockpit workload. Further, VOR approaches provide no vertical guidance, leaving a pilot dependant on another instrument, an altimeter, while also monitoring the timer and performing distance calculations.
The approach methods related to equipment identified above may be divided into two categories, precision approaches and non-precision approaches. A precision approach is one that provides both electronic glideslope information and lateral guidance information. Non-precision approaches provide only lateral guidance information through standard navigational instruments. The glideslope typically refers to the descent profile during the final phase of an aircraft's approach for landing at an airport's runway. Therefore, because no glideslope information is available during a VOR, NDB, or localizer approach, they may be categorized as non-precision approaches. Current GPS approaches may also be non-precision, but procedures for precision GPS approaches may vary based on available equipment. ILS approaches are precision approaches providing both electronic glideslope information and lateral guidance. All of the approach methods utilize navigation radios, tuned to runway specific frequencies, and related cockpit instruments to approach and land using the published procedures. Each of the approach methods also require careful attention of the pilot to ensure that the approach is flown according to information received from the cockpit instruments.
While each approach method has the advantage of allowing a pilot to land where VFR is insufficient, each also has potential problems and difficulties that may increase the cockpit workload for a pilot. Some of these problems are common across the approach methods. For example, a pilot must be certain to tune navigation radios to the proper frequency to navigate to the proper airport. An incorrect frequency can lead to a pilot flying into an area he had no intention of flying into (such as an area with dangerous terrain). Further, to ensure that the navigation radios have been tuned properly, a pilot must quickly recognize the Morse code identifier received from a navigation aid when tuning the radios. During particularly stressful periods in the cockpit (e.g., landing in a thunderstorm), interpreting Morse code can add an additional level of unneeded complication for a pilot.
NDB approaches, while available at nearly all IFR certified airports, present numerous additional problems for pilots. For example, during an NDB approach, a pilot must be mindful of signal interference, twilight error, terrain error, and crosswinds, among other things. A pilot must constantly compensate for any and all of the potential problems to avoid disaster. Further, many pilots are not well trained in use of an auto direction finder (ADF) making NDB approaches particularly difficult to navigate correctly.
Obtaining a fix via VOR, while slightly more accurate than NDB, is generally no easier. To obtain a fix via VOR, two navigation stations must be tuned in and their directions found and plotted on a chart. Further, a VOR approach requires that omni-bearing selector (OBS) knobs be properly turned and aligned on the VOR instruments.
Navigating along lines between NDB or VOR stations can also be a difficult task. Radials change as the aircraft moves, and the preferred way to navigate via NDB or VOR is to plot the course and sample fixes along it before departure. Errors in navigation via NDB or VOR can be very difficult to correct, requiring a fix and then comparing the fix to one of the sample fixes plotted during pre-flight preparation (provided such preparation was completed and completed properly).
ILS approaches, while often the preferred IFR approach because of the availability of electronic glideslope information, utilize both a localizer and an electronic glideslope, introducing additional complexity and uncertainty to the approach. Should any of the equipment malfunction during the approach, the pilot may have to rely on other non-precision approach equipment. Further, should the pilot misread an approach plate and/or mistune a navigation radio, the pilot may be left wondering why the localizer and/or glideslope information is not present, when in fact, the pilot has tuned in the wrong runway or worse, the wrong airport.
Because IFR approach and landing procedures typically vary based on airport, runway, equipment availability (at a particular runway), and time of year, among other things, such procedures are regularly published (e.g., every two weeks) on a navigational chart, typically referred to as an approach plate or approach chart. Approach plates may be published in a variety of forms, and may be named according to the airport for which they were created. It is important that a pilot have reviewed the most recent published version of an approach plate to ensure up-to-date approach procedure information.
Two primary published approach plates, Jeppesen and the National Aeronautical Charting Office (NACO), are the most frequently used. Each of the plates show nearly identical information arranged using different layouts. The approach plates generally provide a pilot with navigation and approach information for each runway at an airport, and the approach plates may also provide surrounding terrain information in selected areas. Approach plates typically provide information including, for example, runway identifiers and configuration (e.g., alignment, available navigation equipment, etc.), navigation radio frequencies, landing minimums (e.g., minimum descent altitude, minimum vectoring altitude, minimum visibilities, etc.), missed approach point, missed approach procedures, critical approach information, altitude information, glideslope (if an ILS), and feeder routes, among other things.
Approach plates may organize approach information by dividing a sheet into several sections. The sections may include an approach plan section, a profile section, a minimums section, and an airport diagram section, among others.
The approach plan section may provide a view similar to a typical navigational chart view and may include airports, waypoints, airways, navigational aid frequencies, and other navigational information related to lateral flight (e.g., east, west, north, and south).
The approach plan view may provide a pilot with two-dimensional lateral guidance for flying an approach and landing in accordance with promulgated procedures for a selected destination airport and runway. Therefore, a pilot must be able to interpret the symbols of the approach plan view quickly and chart aircraft position on the approach plan view to determine additional navigational steps.
The profile section of an approach plate may add depth to the approach plan section by providing the third dimension of altitude. In other words, the profile view may provide vertical guidance as to an aircraft's position relative to the ground and the specified approach procedures. Once again, a pilot must plot the aircraft's current position on the profile view to determine whether an approach segment is being flown at the correct altitude as dictated by the specified procedures.
The minimums section may provide a pilot with information related to minimum altitudes, visibilities, etc., that a pilot must maintain to remain in compliance with the dictated approach procedures. For example, the minimums section may include a minimum descent altitude (MDA), which is the minimum altitude the aircraft may descend to during a non-precision approach before visually verifying the runway. The decision height (DH) is a similar concept related to precision approaches and may also be displayed in the minimums section. The DH may be the altitude on the glideslope at which a pilot must decide whether to continue landing or execute missed approach procedures. It is to be understood that, although not exactly equivalent to MDA, DH and MDA will be used interchangeably, where possible, in the course of this discussion. In another example, the minimums section may include a runway visual range (RVR), which is the minimum length of runway a pilot must be able to see to land on that runway. It is important that a pilot follow these minimums closely to remain in compliance with the approach procedures.
The airport diagram section may provide a pilot with detailed information including the layout of the airport runways, approach hardware, taxiways, amenities, fuel availability, etc. A pilot may use such information to assist in determining which runway/approach combination to select.
Approach plates may be difficult to interpret quickly and require that a pilot study them sufficiently in advance of flight to enable navigation, airport identification, and execution of approach procedures. Further, a pilot must chart aircraft position on both the approach plan section and the profile section of the approach plate continuously to determine the aircraft location relative to the references on the approach plate and whether the aircraft is maintaining flight within the specified approach procedures. Moreover, in the event of a missed approach, a pilot must refer to the approach plate quickly during a period of high stress to gain information allowing a safe exit from the current approach and enabling another attempt to land on the runway.
It may also be necessary from time to time for air traffic control (ATC) to modify specified approach procedures based on current conditions at a particular airport and runway. For example, ATC may determine that landing at a particular airport or runway is not possible (e.g., disabled aircraft on the runway, hardware malfunction, etc.) and may communicate instructions to navigate to another airport or approach another runway with different equipment (e.g., no ILS but only NDB). Because ATC commands take precedence over published approach procedures, a pilot must have related approach plates available and must have the skill and ability to fly an approach as directed by ATC. This may significantly increase cockpit workload and introduce additional levels of difficulty in the approach process.
From the above discussion, it is apparent to one of skill in the art that there is a need for a system and method for determining and displaying navigational information related to the various approach methods to assist pilots in flying an approach to an airport. There is also a need for automatically calculating and displaying an aircraft's position with respect to a published approach plate on a moving map such that a pilot may easily reference the information and adjust the aircraft's navigational parameters accordingly. Moreover, there is a need for a system which can automatically tune navigation radios based on a pre-programmed flight plan and approach parameters. Further, there is a need for a system which can automatically recognize approach parameters communicated by ATC and accurately enter the parameters into an automated system for assisting the pilot in flying a revised approach.
The present disclosure addresses these needs and other related needs in various embodiments of an automated system for displaying approach information on a display device in an aircraft.